Collapsible viewers are well known devices in the art that have been constructed in various shapes and sizes with varying complexity. Some inexpensive viewers are made from rigid or semi-rigid materials such as cardboard or paperboard. Such viewers usually include a pair of optical lenses aligned with and at the proper distance from a pair of stereoscopic images on transparent material (such as slides or film strips) or on opaque material (such as reflection prints). A user holds the viewer up to a light source to allow the light source to illuminate the image to enable seeing a stereo image. The stereoscopic images take on a three-dimensional appearance when the user views them through the optical lenses. Viewing the images through optical lenses provides a level of magnification that is greater than direct (i.e., unaided) viewing of standard-sized reflection prints at a standard viewing distance, thereby providing a more natural viewing perspective that adds realism to the image.
U.S. Pat. No. 4,253,732 relates to a viewer used for viewing several stereo pairs sequentially mounted in the viewer. However, the transparent images or miniature reflection prints utilized in such viewers are of such a small size that they do not allow acceptable direct viewing. Such a viewer does not provide for the viewing of standard-sized two-dimensional reflection prints of the image (for example, 31/2.times.5 inch prints or 4.times.6 inch prints) for the purpose of screening those the user decides to view in stereo. Accordingly, a need continues to exist for a viewer which provides a user with a reflection print of a size comparable to the size of the collapsed viewer for the purpose of easily previewing the image and deciding whether to view it with the viewer to improve its perspective.
Prior art viewers have been constructed as foldable, box-type enclosures that a user must first assemble from a blank. Several U.S. patents, such as U.S. Pat. Nos. 3,734,596, 3,756,699, 4,357,073, 5,136,423, and 4,846,553, describe assembling collapsible stereo viewers from a precursor blank. When expanded, these box-type viewers provide for the surface of each image to be aligned flat and perpendicular to the optical axes of the lenses. There are problems, however, associated with these box-type viewers that have diminished their usefulness. Generally, box-type viewers are constructed from a single cardboard blank having numerous flaps and tabs that must be folded and placed in a proper sequence within appropriate slots that are also formed on the blank. Educating the user of how to properly assemble the viewer may require elaborate instructions. The design of most box-type viewers allows the viewer to be collapsed from the assembled or viewing position to a flattened position for storage. The procedure for collapsing the viewer usually requires performing the assembly steps in reverse. A viewer of complex design will require more elaborate assembly and disassembly steps than a viewer of simple design. Although the user of the viewer may accept this complexity and inconvenience of using the viewer in order to see many stereo images with the same viewer at one sitting, it is unlikely that the user would tolerate having to assemble a different viewer for each different image if the viewer only held one stereo image. Further, the thickness and number of walls or walls making up prior art viewers can also create a collapsed viewer with a thick profile that prevents the viewers from being used in certain applications. Also, although the viewers are collapsible after use, they may not lie perfectly flat but only flatten and remain flattened by a constant compressive force. If the compressive force is removed, the collapsible viewer tends to spring back to a less than truly flattened structure. For these reasons advertisers have refrained from using prior art viewers to advertise their products. Advertisers, greeting card manufacturers, and book publishers appear to be more willing to use collapsible viewers provided that the viewers are relatively inexpensive to manufacture, simple and convenient to use, collapsible to a truly flat profile, and still provide to the user a message or image while in collapsed form. Accordingly, a need continues to exist for a collapsible viewer which is relatively inexpensive to manufacture, simple and convenient to use, collapsible to a truly flat profile, and still provides to the user a message or image while in collapsed form.